Etching composition, method for etching insulating film of semiconductor devices using the same and method for preparing semiconductor devices

ABSTRACT

An etching composition includes phosphoric acid, a silane compound comprising at least one silicon (Si) atom, and an ammonium salt represented by Formula 1 below: 
     
       
         
         
             
             
         
       
         
         
           
             wherein: 
             L 1  to L 3  are independently substituted or unsubstituted hydrocarbylene, 
             R 1  to R 4  are independently hydrogen, a substituted or unsubstituted hydrocarbyl group, and 
             X n−  is an n-valent anion, where n is an integer of 1 to 3.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of priority to Korean Patent ApplicationNo. 10-2019-0109544 filed on Sep. 4, 2019, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to an etching composition, particularly,to an etching composition having a high selectivity ratio, capable ofselectively removing a nitride film while minimizing an etching rate ofan oxide film.

2. Description of Related Art

An oxide film, such as a silicon oxide (SiO₂) film, and a nitride film,such as a silicon nitride (SiNx) film, are representative insulatingfilms. In a semiconductor manufacturing process, the silicon oxide filmand the silicon nitride film are used alone or in a form in which one ormore films are alternately stacked. In addition, the oxide film or thenitride film is also used as a hard mask for forming a conductivepattern such as a metal wiring.

In a wet etching process for removing the nitride film, a mixture ofphosphoric acid and deionized water is generally used. The deionizedwater is added for preventing a decrease in an etching rate and a changein etching selectivity to an oxide film; however, there may be a problemarising in that defects may occur in a nitride film etching removalprocess, even with a minute change in an amount of supplied deionizedwater. In addition, the phosphoric acid is a strong acid and corrosive,thereby leading to difficulties in handling.

In order to solve the above problems, there is a conventionally knowntechnology for removing a nitride film using an etching compositioncontaining fluoric acid (HF), nitric acid (HNO₃), or the like, inphosphoric acid (H₃PO₄). This technology, however, results in reducingan etching selectivity ratio of the nitride film to the oxide film.

Further, there is also a known technology of using an etchingcomposition including phosphoric acid and a silicic acid or a silicate.However, the silicic acid or silicate has a problem of generatingparticles which may affect a substrate, thereby being inappropriate fora semiconductor manufacturing process.

In the meantime, when phosphoric acid is used in a wet etching processfor removing the nitride film, not only the nitride film but also anoxide film such as an SOD oxide film may be etched due to a reducedetching selectivity ratio of the nitride film to the oxide film, wherebyit may be difficult to adjust an effective field oxide height (EFH).Accordingly, a sufficient wet etching time for removing the nitride filmmay not be secured, or an additional process may be required, causing achange and having adverse effects thereon.

Therefore, an etching composition having a high selectivity ratio, whichselectively etches a nitride film to an oxide film and does not have aproblem such as particle generation in a semiconductor manufacturingprocess, is currently demanded.

Meanwhile, a silane-based additive, which is an additive added to aconventional etching composition, has solubility too low to secureoptimal solubility, thereby causing precipitation of particles in theetching solution composition and abnormal growth of a substrate. Suchparticles may remain on a silicon substrate, resulting in a defect of adevice implemented thereon, or in failure of equipment used in anetching or a washing process.

Further, when the etching composition is stored for a long period time,etching speeds of a nitride film and a silicon oxide film changes,thereby varying selection ratio of the nitride film to the oxide film.

SUMMARY

An aspect of the present disclosure is to provide an etching compositionhaving a high selectivity ratio, which can selectively remove a nitridefilm while minimizing etching of an oxide film, without causing problemssuch as particle generation having adverse effects on devicecharacteristics.

Another aspect of the present disclosure is to provide an etchingcomposition having excellent storage stability.

Further, another aspect of the present disclosure is to provide a methodfor etching an insulating film using the etching composition and amethod for manufacturing a semiconductor device.

The present disclosure is to provide an etching composition. Accordingto an embodiment of the present disclosure, an etching compositionincludes phosphoric acid, a silane compound containing at least onesilicon (Si) atom, and an ammonium salt represented by Formula 1:

In Formula 1, L¹ to L³ are independently substituted or unsubstitutedhydrocarbylene, R¹ to R⁴ are independently hydrogen, a substituted orunsubstituted hydrocarbyl group, and X^(n−) is an n-valent anion, wheren is an integer of 1 to 3.

The X may be one selected from the group consisting of a halogen, C₁-C₁₀carboxylate, tosylate, sulfate, mesylate, bisulfate, carbonate,bicarbonate, phosphate, hydrogen phosphate, dihydrogen phosphate andnitrate.

L¹ to L³ may be independently substituted or unsubstituted C₁-C₅alkylene, and are preferably the same. For example, L¹ to L³ may be—CH₂CH₂— or —CH₂CH(CH₃)—.

The hydrocarbyl group may be a substituted or unsubstituted C₁-C₂₀ alkylgroup or a substituted or unsubstituted C₅-C₂₀ aryl group.

For example, R¹ to R³ may be hydrogen, and R⁴ may be hydrogen or aC₁-C₂₀ alkyl group. More specifically, R⁴ may be hydrogen or a —CH₃.

The ammonium salt of Formula 1 may be selected from following StructuralFormulae 1 to 14:

where OAc, OTs and OMs represent acetate, tosylate and mesylate,respectively.

The silane compound may be represented by Formula 2 below:

In Formula 2, R⁵¹ to R⁵⁴ are independently hydrogen, a substituted orunsubstituted hydrocarbyl group or a substituted or unsubstitutedheterohydrocarbyl group, and R⁵¹ to R⁵⁴ exist independently or two ormore thereof form a ring via a heteroatom.

The etching composition of each example embodiment above may include 70wt % to 95 wt % of the phosphoric acid, 0.001 wt % to 5 wt % of thesilane compound and 0.001 wt % to 10 wt % of the ammonium saltrepresented by Formula 1.

The present disclosure provides a method for etching an insulating filmusing the etching composition described above, and a method forpreparing a semiconductor device including the method for etching aninsulating film.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1 and 2 are exemplary process cross-sectional views illustrating adevice separation process of a flash memory device.

DETAILED DESCRIPTION

The present disclosure is to provide an etching composition, inparticular, an etching composition having a high selectivity ratioenabling selective removal of a nitride film while minimizing etching ofan oxide film and having excellent storage stability.

The etching composition of the present disclosure includes phosphoricacid. The phosphoric acid may react with silicon nitride to etch asilicon nitride film, and react with the silicon nitride as in Equation(1) below:3Si₃N₄+27H₂O+4H₃PO₄→4(NH₄)₃PO₄+9SiO₂H₂O  (1).

The etching composition of the present disclosure includes an ammoniumsalt represented by Formula 1 below:

In Formula 1, L¹ to L³ are independently substituted or unsubstitutedhydrocarbylene. L¹ to L³ may be independently substituted orunsubstituted C₁-C₅ alkylene, for example, —CH₂CH₂— or —CH₂CH(CH₃)—. L¹to L³ may be different from each other or the same.

In Formula 1, R¹ to R⁴ are independently hydrogen, a substituted orunsubstituted hydrocarbyl group. The substituted or unsubstitutedhydrocarbyl group may be a substituted or unsubstituted C₁-C₂₀ alkylgroup or a substituted or unsubstituted C₅-C₂₀ aryl group. R¹ to R⁴ maybe different from each other, or two or more thereof may be the same.For example, R¹ to R³ may be hydrogen, and R⁴ may be hydrogen or aC₁-C₂₀ alkyl group.

In Formula 1, X^(n−) may be an n-valent anion, and preferably where n isan integer of 1 to 3. For example, the X may be a halogen, such as F,Cl, Br, I, or the like. X may also be one selected from the groupconsisting of C₁-C₁₀ carboxylate such as an acetate, tosylate, sulfate,mesylate, bisulfate, carbonate, bicarbonate, phosphate, hydrogenphosphate, dihydrogen phosphate and nitrate.

The ammonium salt represented by Formula 1 provided in the presentdisclosure provides structural stability to the silane compound andprevents decomposition or abnormal growth of the silane compound tosuppress particle formation of the etching compound and etching of thesilicon oxide.

The ammonium salt contained in the etching composition may be used aloneas long as it is represented by Formula 1 above, or two or more thereofmay be mixed to use.

The ammonium salt employed in the present disclosure may be an ammoniumsalt of the following structures (1) to (14):

where OAc, OTs and OMs represent acetate, tosylate and mesylate,respectively.

The ammonium salt of Formula 1 may prevent particle formation of theetching composition and may be added in an amount of 0.001 wt % to 10 wt% based on a total weight of the etching composition. When the ammoniumsalt is added in an amount of less than 0.001 wt %, it is difficult toobtain an effect of suppressing particle formation, whereas if theamount exceeds 10 wt %, the ammonium salt may accelerate particleformation.

A content of the ammonium salt of Formula 1 may be, for example, 0.001to 5 wt %, 0.001 to 3 wt %, 0.001 to 2 wt %, 0.001 to 1 wt %, 0.005 to 5wt %, 0.005 to 3 wt %, 0.005 to 2 wt %, 0.005 to 1 wt %, 0.01 to 5 wt %,0.01 to 3 wt %, 0.01 to 2 wt %, 0.01 to 1 wt %, 0.05 to 5 wt %, 0.05 to3 wt %, 0.05 to 2 wt %, 0.05 to 1 wt %, 0.1 to 5 wt %, 0.1 to 3 wt %,0.1 to 2 wt %, 0.1 to 1 wt %, 0.5 to 5 wt %, 0.5 to 3 wt %, 0.5 to 2 wt% or 0.5 to 1 wt %.

The etching composition includes a silane compound. Any silane compoundcontaining one or more silicon atoms may be appropriately used in thepresent disclosure. More preferably, the silane compound may be a silanecompound represented by Formula 2 below:

In Formula 2, R⁵¹ to R⁵⁴ are independently hydrogen, a substituted orunsubstituted hydrocarbyl group, such as a substituted or unsubstitutedC₁-C₂₀ hydrocarbyl group, or a substituted or unsubstitutedheterohydrocarbyl group, such as a substituted or unsubstituted C₁-C₂₀heterohydrocarbyl group. R⁵¹ to R⁵⁴ may exist independently, or two ormore thereof may form a ring connected by a heteroatom. For example, R⁵¹to R⁵⁴ may be hydrogen, a substituted or unsubstituted C₁-C₂₀ alkylgroup, a substituted or unsubstituted C₁-C₂₀ heteroalkyl group, or thelike. In this case, the heteroatom is not particularly limited, but maybe N, S, O, P, or the like.

The silane compound represented by Formula 2 may be included in anamount of 0.005 wt % to 1 wt %, based on a total weight of the etchingcomposition.

Further, the etching composition may further include an additionalammonium salt, in addition to the ammonium salt represented by Formula1.

The ammonium salt is a compound having an ammonium ion, and any of thoseconventionally used in the art may be appropriately used in the presentdisclosure. Although not particularly limited, the ammonium salt may be,for example, ammonia water, ammonium chloride, ammonium acetate,ammonium phosphate, ammonium peroxydisulfate, ammonium sulfate, ammoniumfluorate, or the like. These may be used alone or in a combination oftwo or more thereof.

Furthermore, the etching composition of the present disclosure mayfurther contain an optional additive conventionally used in the art tofurther improve etching performance. The additive may be a surfactant, ametal ion sequestrant, a corrosion inhibitor, or the like.

The etching composition of the present disclosure is used for selectiveremoval of a nitride film by etching from a semiconductor deviceincluding an oxide film and the nitride film. The nitride film mayinclude a silicon nitride film, for example, a SiN film, a SiON film, orthe like.

In addition, the oxide film may be at least one selected from the groupconsisting of a silicon oxide film, for example, a spin on dielectric(SOD) film, a high density plasma (HDP) film, a thermal oxide film, aborophosphate silicate glass (BPSG) film, a phosphosilicate glass (PSG)film, a borosilicate glass (BSG) film, a polysilazane (PSZ) film, afluorinated silicate glass (FSG) film, a low pressure tetraethylorthosilicate (LPTEOS) film, a plasma enhanced tetraethyl orthosilicate(PETEOS) film, a high temperature oxide (HTO) film, a medium temperatureoxide (MTO) film, an undoped silicate glass (USG) film, a spin on glass(SOG) film, an advanced planarization layer (APL) film, an atomic layerdeposition (ALD) film, a plasma enhanced oxide (PE-oxide) film, anO3-tetraethyl orthosilicate (O3-TEOS) film or combinations thereof.

An etching method involving use of the etching composition of thepresent disclosure may be performed by a wet etching method, forexample, dipping, spraying, or the like.

An example of an etching process using the etching composition of thepresent disclosure is schematized in FIGS. 1 and 2. FIGS. 1 and 2 areexemplary process cross-sectional views illustrating a device separationprocess of a flash memory device.

As illustrated in FIG. 1, a tunnel oxide film 11, a polysilicon film 12,a buffer oxide film 13 and a pad nitride film 14 are formed on asubstrate 10 in said order, and the polysilicon film 12, the bufferoxide film 13 and the pad nitride film 14 are then selectively etched toform a trench. Subsequently, an SOD oxide film 15 is formed until thetrench is gap-filled, and a CMP process is then carried out on the SODoxide film 15 using the pad nitride film 14 as a polishing stop film.

As illustrated in FIG. 2, after the pad nitride film 14 is removed bywet etching using a phosphoric acid solution, the buffer oxide film 13is removed in a washing process. As a result, a device separation film15A is formed in a field area.

A temperature of the etching process may be in a range of 50° C. to 300°C., preferably 100° C. to 200° C., more preferably 156° C. to 163° C.,and an appropriate temperature may be changed, if necessary, inconsideration of other processes and factors.

As such, according to a method for manufacturing a semiconductor deviceincluding the etching process carried out using the etching compositionof the present disclosure, selective etching of the nitride film isfeasible when the nitride film and the oxide film are alternatelystacked or mixed. In addition, stability and reliability of the processcan be secured by preventing the generation of particles, which wasproblematic in the conventional etching process.

Accordingly, such a method may be efficiently applied to variousprocesses requiring selective etching of the nitride film to the oxidefilm in the semiconductor device manufacturing process.

EXAMPLE

Hereinafter, the present disclosure will be described in detail by wayof examples. The following Examples relate to an example of the presentdisclosure, but the present disclosure is not limited thereto.

Synthesis Example 1

10 g of triethanolamine was added to a 100 mL round bottom flask,followed by adding 30 mL of ethanol, and stirred.

The mixture was cooled until reaching 0° C. while maintaining an N₂atmosphere, and 4.1 g of acetic acid was gradually added. A temperatureoutside of the flask was increased to 90° C., and the mixture wasreacted under reflux for 24 hours.

The external temperature was lowered to 40° C., and the ethanol wasremoved by distillation under reduced pressure. Vacuum drying was thenperformed for 12 hours to obtain an ammonium salt additive 1 of Formula1 below:

¹H-NMR (DMSO-d6): 5.00 (broad, 4H), 3.71 (t, 6H), 2.67 (t, 6H), 1.98 (s,3H)

Synthesis Example 2

10 g of triethanolamine was added to a 100 mL round bottom flask,followed by adding 30 mL of acetonitrile, and stirred.

The mixture was cooled until reaching 0° C. while maintaining an N₂atmosphere, and 4.3 g of dimethylsulfate was gradually added. Atemperature outside of the flask was increased to 90° C., and themixture was reacted under reflux for 60 hours.

The external temperature was lowered to 25° C., and a layer of theacetonitrile was removed, followed by adding another 30 mL ofacetonitrile to the flask to wash-remove the same.

Vacuum drying was then performed for 12 hours to obtain an ammonium saltadditive 2 of Formula 2 below:

¹H-NMR (DMSO-d6): 4.78 (broad, 3H), 3.81 (m, 6H), 3.49 (t, 6H), 3.12 (s,3H)

Synthesis Example 3

5 g of triisopropanolamine was added to a 100 mL round bottom flask,followed by adding 30 mL of ethanol, and stirred.

The mixture was cooled until reaching 0° C., and 1.65 mL of 70% nitricacid was gradually added. A temperature outside of the flask wasincreased to 90° C., and the mixture was reacted under reflux for 20hours.

The external temperature was lowered to 50° C., and the ethanol wasremoved by distillation under reduced pressure. 50 mL of toluene wasadded to a resulting concentrated residue and distilled again underreduced pressure. Vacuum drying was then performed for 24 hours toobtain an ammonium salt additive 3 of Formula 3 below:

¹H-NMR (DMSO-d6): 4.94 (broad, 4H), 3.78 (m, 3H), 2.61 (m, 6H), 1.31 (m,9H)

Synthesis Example 4

10 g of triisopropanolamine was added to a 100 mL round bottom flask,followed by adding 30 mL of ethanol, and stirred.

The mixture was cooled until reaching 0° C., and 9.7 g of methylp-toluenesulfonate was gradually added. A temperature outside of theflask was increased to 90° C., and the mixture was reacted under refluxfor 24 hours.

The external temperature was lowered to 50° C., and the ethanol wasremoved by distillation under reduced pressure. 50 mL of acetone wasadded to a resulting concentrated residue and distilled again underreduced pressure. Vacuum drying was then performed for 24 hours toobtain an ammonium salt additive 4 of Formula 4 below:

¹H-NMR (DMSO-d6): 7.48 (d, 2H), 7.12 (d, 2H), 5.05 (broad, 3H), 3.69 (m,3H), 2.59 (m, 6H), 2.28 (s, 3H), 1.42 (m, 9H)

Example 1

A substrate on which a silicon oxide (SiOx) film deposited at athickness of 500 angstroms (Å) and a silicon nitride (SiN) filmdeposited at a thickness of 5000 Å was prepared on a semiconductorwafer.

As shown in Table 1, 99.4 wt of phosphoric acid with 85% concentration,0.5 wt % of 3-aminopropylsilanetriol, and 0.1 wt % of the ammonium saltadditive 1 were added and mixed to prepare an etching composition suchthat a total weight percentage becomes 100 wt %.

Examples 2 to 4

The same method used in Example 1 was used to prepare an etchingcomposition, except that ammonium salt additives 2 to 4 were used.

Comparative Example 1

The same method used in Example 1 was used to prepare an etchingcomposition, except that no ammonium salt additive was used.

Comparative Example 2

The same method used in Example 1 was used to prepare an etchingcomposition, except that ammonium acetate ((NH₄) OAc) was used as anammonium salt additive.

<Preparation of Etching Composition and Measurement of Selection Ratio>

Each of the etching compositions obtained in Examples 1 to 4 andComparative Example 1 was added to a round flask, heated for 60 minutesto heat up to 158° C. The silicon wafer was then dipped into the etchingcomposition for 720 seconds and 6000 seconds to perform an etchingprocess.

A surface of the silicon wafer, on which a pattern was formed, wasselectively etched, and thicknesses of the silicon oxide film and thesilicon nitride film before and after etching were measured usingEllipsometry, thin film thickness measurement equipment (NANO VIEW,SEMG-1000). Based thereon, an etching speed of the silicon oxide film(SiO E/R, Å/min) and that of the nitride film (SiN E/R, Å/min) as wellas selection ratios thereof were calculated, and a result thereof isshown in Table 1.

The selection ratio represents a ratio of a nitride film etching speedto an oxide film etching speed, and the etching speed is a valuecalculated by dividing a difference in the film thicknesses before andafter etching by an etching time (minute).

TABLE 1 Composition (wt %) Ammonium 85% salt Process Etching phosphoric3-aminopropyl additive temp. SiN E/R SiO E/R selectivity acidsilanetriol No./content (° C.) (Å/min) (Å/min) Ratio CE 1 99.5 0.5 wt %— 158 68.3 0.32 213 CE 2 99.4 0.5 wt % (NH₄)OAc/ 158 72.7 0.21 346 0.1wt % EX 1 99.4 0.5 wt % 1/0.1 wt % 158 87.9 0.12 733 EX 2 99.4 0.5 wt %2/0.1 wt % 158 87.3 0.11 794 EX 3 99.4 0.5 wt % 3/0.1 wt % 158 85.6 0.09951 EX 4 99.4 0.5 wt % 4/0.1 wt % 158 91.3 0.15 609 *CE: ComparativeExample **EX: Example

As shown in Table 1 above, it can be understood that remarkably highetching selectivity ratios are exhibited when ammonium salt additives 1to 4 are added to the etching composition as an additive, as compared toComparative Examples 1 and 2. Further, in terms of the silicon nitrideetching speed (SiN E/R), the etching compositions of Examples 1 to 4exhibited a remarkably excellent effect as compared to that ofComparative Examples 1 and 2. As a result, it is confirmed that anetching composition optimized for an etching process of a siliconnitride film can be provided.

Based on the results, it is confirmed that use of the ammonium saltssuggested in the present disclosure as additives may lead to improvedactive silicon-based structural stability. Accordingly, an etchingcomposition having an improved etching speed of a silicon nitride film,a selection ratio and etching stability can be provided.

[Change in Etching Composition Over Time]

The etching compositions of Comparative Example 1 and Example 1 werestored at about 70° C. for a predetermined period of time and subject toan etching test every 7 days under the same conditions. A result thereofis shown in Table 2.

TABLE 2 Period of SiN E/R SiO E/R Selection storage (Å/min) (Å/min)ratio Comparative — 68.3 0.32 213 Example 1  7 days 66.7 0.35 191 14days 65.1 0.36 181 21 days 61.3 0.39 157 Example 1 — 87.9 0.12 733  7days 87.2 0.12 727 14 days 86.6 0.12 722 21 days 86.5 0.12 721

As shown in Table 2 above, the etching composition of ComparativeExample 1 after 21 days showed significantly reduced etching speeds (SiNE/R) and selection ratio. However, the etching composition of Example 1,to which the ammonium salt additive 1 is added, showed almost no changein the etching speeds (SiN E/R) and selection ratio. This indicates thatthe etching composition according to an embodiment of the presentdisclosure has not only excellent etching speeds and selection ratio butalso excellent storage stability, and thus can maintain superior etchingcharacteristics even when stored for a long period of time.

Such results also indicate that the structural stability effect ofammonium salt additive 1 can maintain the function of inhibiting etchingof SiO without abnormal growth or decomposition of3-aminopropylsilanetriol.

According to the aforementioned example embodiments, the etchingcomposition according to the present disclosure has a high etchingselectivity ratio of a nitride film to an oxide film.

In addition, use of the etching composition of the present disclosuremay prevent damage of film quality of the oxide film when removing thenitride film or deterioration of electric characteristics due to etchingof the oxide film, as well as preventing generation of particles,thereby improving device characteristics.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. An etching composition, comprising: 70 wt % to 95wt % of phosphoric acid, a silane compound containing at least onesilicon (Si) atom, and an ammonium salt represented by Formula 1 below:

wherein: L¹ to L³ are independently substituted or unsubstitutedhydrocarbylene, R¹ to R⁴ independently hydrogen, a substituted orunsubstituted hydrocarbyl group, and X^(n−) is an n-valent anion, wheren is an integer of 1 to
 3. 2. The etching composition of claim 1,wherein X is one selected from the group consisting of a halogen, C₁-C₁₀carboxylate, tosylate, sulfate, mesylate, bisulfate, carbonate,bicarbonate, phosphate, hydrogen phosphate, dihydrogen phosphate andnitrate.
 3. The etching composition of claim 1, wherein L¹ to L³ areindependently substituted or unsubstituted C₁-C₅ alkylene.
 4. Theetching composition of claim 3, wherein L¹ to L³ are the same.
 5. Theetching composition of claim 4, wherein L¹ to L³ are —CH₂CH₂—or—CH₂CH(CH₃)—.
 6. The etching composition of claim 1, wherein thehydrocarbyl group is a substituted or unsubstituted C₁-C₂₀ alkyl groupor a substituted or unsubstituted C₆-C₂₀ aryl group.
 7. The etchingcomposition of claim 1, wherein R¹ to R³ are hydrogen, and R⁴ ishydrogen or a C₁-C₂₀ alkyl group.
 8. The etching composition of claim 7,wherein R⁴ is hydrogen or a —CH₃.
 9. The etching composition of claim 1,wherein Formula 1 is selected from following Structural Formulae 1 to14:

where OAc, OTs and OMs represent acetate, tosylate and mesylate,respectively.
 10. The etching composition of claim 1, wherein the silanecompound is represented by Formula 2 below:

wherein, in Formula 2, R⁵¹ to R⁵⁴ are independently hydrogen, asubstituted or unsubstituted hydrocarbyl group or a substituted or runsubstituted heterohydrocarbyl group, and R⁵¹ to R⁵⁴ existindependently or two or more thereof form a ring via a heteroatom. 11.The etching composition of claim 1, comprising 70 wt % to 95 wt % of thephosphoric acid, 0.001 wt % to 5 wt % of the silane compound and 0.001wt % to 10 wt % of the ammonium salt represented by Formula
 1. 12. Amethod for etching an insulating film using the etching composition ofclaim
 1. 13. A method for preparing a semiconductor device, comprising:forming a tunnel oxide film, a polysilicon film, a buffer oxide film anda pad nitride film on a substrate in said order; forming a trench byselectively etching the polysilicon film, the buffer oxide film and thepad nitride film; forming an SOD oxide film to gap-fill the trench;performing a chemical mechanical polishing (CMP) process on the SODoxide film using the pad nitride film as a polishing stop film; removingthe pad nitride film by wet etching using the etching composition ofclaim 1; and removing the buffer oxide film.